5177. Yield of MR-Directed Ultrasound for MRI-Detected Breast Findings: How Often Can We Avoid MR Biopsy?
Authors * Denotes Presenting Author
  1. Xiaoxuan Emily Chen *; Weill Cornell Medical College
  2. Melissa Reichman; Weill Cornell Medicine
  3. Annabel Lee; Weill Cornell Medical College
  4. Julia Losner; Weill Cornell Medical College
  5. Charlene Thomas; Weill Cornell Medicine/Population Health Sciences
  6. Janine Katzen; Weill Cornell Medicine
MR-directed ultrasound (US) is frequently performed for suspicious findings identified on breast MRI, secondary to the relative decreased cost and patient-associated discomfort associated with US-guided biopsies compared to MRI-guided biopsies. However, performing MR-directed US on low-yield findings can lead to unnecessary delays. The purpose of this study was to evaluate the yield of MR-directed US for MRI-detected breast findings and to determine if there are a subset of findings that have a higher yield.

Materials and Methods:
In this retrospective single-center study, we identified 857 consecutive patients who had a breast MRI between January 2017 to December 2020. Only exams which received a BI-RADS 4 or 5 assessment and were recommended for MR-directed US were included in the study, yielding 765 patients. Included findings were further characterized by presence or absence of a sonographic correlate. Utilizing the EMR, for those with a sonographic correlate, the size, location, and morphology of breast findings were noted. Imaging-guided (US and MRI) pathology results, as well as excisional pathology results were recorded. In addition, patient demographics were obtained. A multivariable logistical regression analysis was used to investigate the clinical utility of an MR-directed US.

There were 1262 MRI-detected BI-RADS category 4 or 5 findings in 765 patients. Of the 1262 findings, MR-directed US was performed on 852 (68%). Of these 852 findings, 291 (34%) had an US correlate, including 143 (49%) benign lesions, 81 (28%) malignant lesions, 16 (5%) with high-risk pathology, and 51 (18%) unknown (lost to follow-up). Of those findings with US correlates, 173 (59%) represented masses, 69 (24%) were regions of non-mass enhancement (NME), 22 (7.6%) were foci, and 27 (9.3%) fell into the category of other, which included lymph node, cysts, and scar tissue. Masses were significantly more likely to be identified on MR-directed US (<em>p</em> < 0.0001) compared to foci. When determining the yield of MR-directed US based on the imaging finding, 44% (173/394) of masses, 23% (69/295) of NME, and 17% (22/130) of foci had an US correlate.

MR-directed US has the benefit of decreased cost and discomfort for the patient when a sonographic correlate is found, and US guided biopsy can be performed. However, it is important to be aware of the yield of MR-directed US for different MR findings to prevent delays in care. The yield of MR-directed US is significantly higher for masses than for foci. The likelihood of a sonographic correlate should be taken into consideration when recommending MR-directed US in these patients.